1. Field of the Invention
The invention relates to a film formation system and film formation method for forming a metal film and, more particularly, to a film formation system and film formation method that are able to form a thin metal film uniformly on a surface of a substrate.
2. Description of Related Art
Generally, when an electronic circuit substrate, or the like, is manufactured, a metal film is formed on the surface of a substrate in order to form a metal circuit pattern. For example, as a film formation technique for forming such a metal film, there has been suggested a film formation technique for forming a metal film on the surface of a semiconductor substrate, such as Si, by plating, such as electroless plating (see, for example, Japanese Patent Application Publication No. 2010-037622 (JP 2010-037622 A)) or forming a metal film by a PVD method, such as sputtering.
However, when the plating, such as electroless plating, is performed, the plated substrate needs to be washed in water, so it is required to treat waste liquid used in water washing. When a film is formed on the surface of the substrate by the PVD method, such as sputtering, internal stress develops in the coated metal film, so there is a limit to increase the thickness of the film, and, particularly, in the case of sputtering, there are cases where the film is allowed to be formed only in a high vacuum.
In terms of such a point, for example, a film formation method for forming a metal film has been suggested (see, for example, Japanese Patent Application Publication No. 2012-219362 (JP 2012-219362 A)). The film formation method uses an anode, a cathode, a solid electrolyte membrane and a power supply unit. The solid electrolyte membrane is arranged between the anode and the cathode. The power supply unit applies voltage between the anode and the cathode.
The solid electrolyte membrane is formed by spin-coating a solution containing a precursor of the solid electrolyte membrane on the surface of a substrate and curing the solution in advance. Metal ions to be coated are impregnated in the solid electrolyte membrane. The substrate is arranged opposite the anode so as to be electrically conductive with the cathode. The metal ions impregnated inside the solid electrolyte membrane are precipitated at a cathode side by applying voltage between the anode and the cathode. Thus, it is possible to form a metal film made of a metal of the metal ions.
However, when the technique described in JP 2012-219362 A is used, a film is formed while bringing the solid electrolyte membrane into contact with the substrate without any gap, so gas (hydrogen gas) is produced as a by-product between the solid electrolyte membrane and the substrate (metal film), and the gas remains in the metal film in a compressed state in process of film formation. The remaining gas becomes a factor developing a defect, such as a void and a pinhole, in the metal film.